A holosystolic murmur is a heart sound that lasts the entire time the heart’s lower chambers are squeezing, stretching from the first heart sound (S1) all the way to the second heart sound (S2). It signals that blood is flowing backward through a leaky valve or through a hole between the heart’s two pumping chambers. The term “pansystolic” means the same thing and is used interchangeably.
Why the Sound Lasts All of Systole
Most heart murmurs happen because blood is being pushed through a narrow or abnormal opening. What makes a holosystolic murmur distinct is that the pressure difference driving that abnormal flow stays relatively constant from the moment the heart starts contracting until it relaxes. In a normal heartbeat, the lower chambers (ventricles) build pressure, open the outflow valves, eject blood, and then relax. A holosystolic murmur occurs while those outflow valves are still closed, because blood is escaping in the wrong direction the entire time the ventricle is squeezing.
Because the pressure gradient between the leaking chamber and the receiving chamber remains high and steady, the sound typically has a “plateau” shape. It doesn’t crescendo or fade in the middle. It starts right at S1, stays at roughly the same loudness, and continues to S2 or even slightly past it.
Three Main Causes
Holosystolic murmurs come from one of three conditions: a leaky mitral valve, a leaky tricuspid valve, or a ventricular septal defect (a hole in the wall between the left and right ventricles).
Mitral Regurgitation
The mitral valve sits between the left atrium and left ventricle. When it doesn’t close properly, blood leaks backward into the left atrium every time the ventricle contracts. The resulting murmur is high-pitched and blowing, heard best at the lower left tip of the heart (the apex), and it often radiates toward the left armpit. Mitral regurgitation is the most common cause of a holosystolic murmur and becomes increasingly prevalent with age. A 2025 systematic review in the Journal of Clinical Medicine estimated that moderate-to-severe mitral regurgitation affects about 0.63% of people at age 50, rising to roughly 2.85% at 70 and 6.45% by age 90.
Tricuspid Regurgitation
The tricuspid valve separates the right atrium and right ventricle. When it leaks, the murmur is also high-pitched and blowing but is heard best along the lower left edge of the breastbone. Unlike mitral regurgitation, tricuspid regurgitation typically doesn’t radiate far from that spot. The key distinguishing feature: the tricuspid murmur gets louder when you breathe in, because inhaling draws more blood into the right side of the heart and increases the volume of the backward leak.
Ventricular Septal Defect
A ventricular septal defect (VSD) is a hole in the muscular wall dividing the two ventricles. Blood shunts from the higher-pressure left ventricle into the right ventricle. The murmur is best heard at the lower left sternal border, similar to tricuspid regurgitation, but has a harsher quality. Counterintuitively, small holes produce louder, harsher murmurs because blood is forced through a tighter opening at higher velocity. Larger defects generate softer murmurs. VSDs are one of the most common congenital heart defects and are often detected in infancy.
What a Holosystolic Murmur Sounds Like
The classic description is a “blowing” sound, like air moving steadily through a narrow space. It maintains roughly the same volume from start to finish rather than swelling and fading. Clinicians grade murmur intensity on a 1-to-6 scale:
- Grade 1: Barely audible, easy to miss
- Grade 2: Soft but detectable with a stethoscope
- Grade 3: Easily heard, no vibration felt on the chest
- Grade 4: Loud with a palpable vibration (thrill) on the chest wall
- Grade 5: Audible with the stethoscope barely touching the skin
- Grade 6: Audible with the stethoscope lifted off the chest entirely
A holosystolic murmur graded 3 or higher is more likely to reflect significant heart disease. The pitch of the murmur is proportional to the pressure difference across the abnormal opening: a bigger pressure gap means a higher-pitched sound.
How Clinicians Tell the Causes Apart
Because all three conditions produce murmurs in the same phase of the heartbeat, location and simple physical maneuvers help narrow the diagnosis. Mitral regurgitation is loudest at the apex and radiates to the armpit. Tricuspid regurgitation is loudest at the lower left sternal border and gets louder with deep inspiration. A VSD murmur is also heard at the lower left sternal border but has a distinctly harsh, rough quality rather than a blowing one.
Certain movements change the loudness of the murmur in predictable ways. Squatting or squeezing the fists (isometric handgrip) increases resistance in the blood vessels, which forces more blood backward through a leaky mitral valve and makes that murmur louder. Standing up or performing a Valsalva maneuver (bearing down as if straining) reduces blood return to the heart and makes mitral regurgitation quieter. If the murmur gets louder when you breathe in, it almost certainly involves the tricuspid valve.
When a Holosystolic Murmur Is Concerning
Not every murmur means trouble, but holosystolic murmurs carry more clinical weight than many other types. The American Academy of Family Physicians considers a holosystolic murmur one of several “red flags” that increase the likelihood the murmur is pathologic rather than innocent. Other warning signs include a grade 3 or louder murmur, a harsh quality, an abnormal second heart sound, or accompanying symptoms like shortness of breath with exertion, swelling in the legs or ankles, or frequent respiratory infections (particularly in infants with a VSD).
An echocardiogram (heart ultrasound) is the standard next step after a holosystolic murmur is heard on exam. It shows the structure and movement of the valves, measures how much blood is leaking, and can identify a septal defect directly. This imaging gives a far more precise picture than listening alone and determines whether the leak is mild enough to monitor or severe enough to need intervention.
How It Differs From Other Systolic Murmurs
Not all murmurs heard during systole are holosystolic. A crescendo-decrescendo murmur, sometimes called a “diamond-shaped” murmur, swells in the middle of systole and then fades. This pattern is typical of aortic stenosis (a stiff, narrowed outflow valve) and many innocent flow murmurs. It sounds fundamentally different from the steady, plateau-shaped holosystolic murmur. Late systolic murmurs, which begin partway through systole, often follow a click and suggest mitral valve prolapse, where the valve bows backward before it starts leaking.
The timing matters because it points directly to the underlying problem. A murmur that fills all of systole with a constant intensity tells a clinician that blood is escaping backward through a valve or septum the entire time the ventricle is contracting, which is a different mechanical problem from a valve that’s too narrow to let blood flow forward efficiently.